1. Field of the Invention
The present invention relates to a lens barrel that moves a lens unit using a vibration actuator.
2. Description of the Related Art
Conventionally, a vibration actuator in which an object to be driven contacts a vibration body configured by a vibration element such as a piezoelectric element to vibrate this vibration body to relatively move a moving lens unit by a friction of a pressure contact portion for the movable lens in a lens barrel has been known. This vibration actuator may generate abrasion powders at the pressure contact portion by the slide of the vibration body and the object to be driven.
Japanese Patent Laid-Open No. 2008-167561 discloses a rotating type vibration actuator. However, when the rotating type vibration actuator as disclosed in Japanese Patent Laid-Open No. 2008-167561 is used, a conversion mechanism such as cam slope that couples for a cam pin of converting a rotating motion into a translatory movement is necessary. Therefore, a whole size of the apparatus is enlarged. Furthermore, if the moving lens unit needs to move at high speed, a rating ring needs to rotate at higher speed and the energy efficiency is reduced, and also a problem that generates a noise or the like may occur due to the high-speed rotation of the rotating ring.
Japanese Patent No. 3170999 discloses a configuration in which a moving lens unit is moved in an optical axis direction using a direct acting type vibration actuator that moves along a drive shaft extending in the optical axis direction. When the direct acting type vibration actuator is used, the growth in size of the whole of the apparatus can be avoided compared to a case where a rotating ring type actuator is used because an object to be driven moves in the moving direction integrally with the moving lens unit. In addition, since a conversion member that is needed for the rotating ring type actuator is not necessary, energy efficiency is good and a silent lens barrel can be provided.
However, the direct acting type vibration actuator changes a position of the pressure contact portion in accordance with a position of the moving lens unit. Therefore, it is difficult to cover a space that contains the pressure contact portion for the purpose of preventing the scatter of the abrasion powders.
In the direct acting type vibration actuator that is disclosed in Japanese Patent No. 3170999, the drive shaft that is a vibration body and the pressure contact portion of the object to be driven are exposed. Therefore, the abrasion powders generated at the pressure contact portion are scattered to a lens or an optical element such as an image sensor, and a harmful influence on an output image may be made.